Buck converters are used as step down voltage regulators. The converters provide an output current through a series inductor that is usually driven by two switching transistors, one of which is connected to supply current to the inductor, and the other connected to draw current from the inductor. Because the buck converter is a switching type regulator the output voltage regulation is influenced by fluctuations in the input voltage to the regulator. Therefore, it is desirable to attenuate any fluctuations in the input voltage at the connections to the switching transistors.
The active devices of a buck converter, because of its relative simplicity compared to normal voltage regulators, can be integrated in a single molded package and therefore are often used in small electronic devices. However, there are other passive components needed for the converter, and integration of any one of these components into the molded package would be advantageous.